Difference between revisions of "RosettaCode Monty Hall"
Peter gummer (Talk | contribs) (→Eiffel code) |
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==Eiffel code== | ==Eiffel code== | ||
| + | |||
| + | Here's an initial implementation, just to get things started. I just typed this straight into the wiki, so it might not even compile. | ||
| + | |||
| + | Please feel free to edit this in place, I won't be offended. | ||
| + | |||
| + | <e> | ||
| + | class MONTY_HALL | ||
| + | |||
| + | feature | ||
| + | |||
| + | play | ||
| + | local | ||
| + | games: INTEGER | ||
| + | random: RANDOM | ||
| + | doors: ARRAYED_LIST [BOOLEAN] | ||
| + | chosen, shown: INTEGER | ||
| + | stayWins: INTEGER | ||
| + | do | ||
| + | games := 1000000 | ||
| + | create random.make | ||
| + | |||
| + | across 1 |..| games as plays loop | ||
| + | create doors.make_filled (3) -- False is a goat, True is a car | ||
| + | random.forth | ||
| + | doors [random.item \\ 3 + 1] := True -- Put a car behind a random door | ||
| + | |||
| + | random.forth | ||
| + | chosen := random.item \\ 3 + 1 -- Pick a door, any door | ||
| + | |||
| + | from shown := chosen until shown /= chosen and not doors [shown] loop | ||
| + | random.forth | ||
| + | shown := random.item \\ 3 + 1 | ||
| + | end | ||
| + | |||
| + | if doors [chosen] then -- If you would have won by staying, count it | ||
| + | stay_wins := stay_wins + 1 | ||
| + | end | ||
| + | end | ||
| + | |||
| + | out ("Staying wins " + stay_wins + " times.%N") | ||
| + | out ("Switching wins " + games - stay_wins + " times.%N") | ||
| + | end | ||
| + | |||
| + | end | ||
| + | |||
| + | </e> | ||
| + | |||
| + | Note that the implementations in many other languages maintain a separate variable to count the number of switch wins. They calculate whether switching wins at each step via some funky logic that relies on zero-based array indexing, which would be inconvenient in Eiffel. But we don't need to do that at all anyway, because calculating it at each step is completely redundant: we can just do a final subtraction at the end, right? | ||
==Comments== | ==Comments== | ||
Revision as of 16:14, 9 August 2012
Reference
Statement of the Monty Hall problem on RosettaCode: here.
Deadline for adding to RosettaCode page: 31 Aug 2012; submitter:
Eiffel code
Here's an initial implementation, just to get things started. I just typed this straight into the wiki, so it might not even compile.
Please feel free to edit this in place, I won't be offended.
class MONTY_HALL feature play local games: INTEGER random: RANDOM doors: ARRAYED_LIST [BOOLEAN] chosen, shown: INTEGER stayWins: INTEGER do games := 1000000 create random.make across 1 |..| games as plays loop create doors.make_filled (3) -- False is a goat, True is a car random.forth doors [random.item \\ 3 + 1] := True -- Put a car behind a random door random.forth chosen := random.item \\ 3 + 1 -- Pick a door, any door from shown := chosen until shown /= chosen and not doors [shown] loop random.forth shown := random.item \\ 3 + 1 end if doors [chosen] then -- If you would have won by staying, count it stay_wins := stay_wins + 1 end end out ("Staying wins " + stay_wins + " times.%N") out ("Switching wins " + games - stay_wins + " times.%N") end end
Note that the implementations in many other languages maintain a separate variable to count the number of switch wins. They calculate whether switching wins at each step via some funky logic that relies on zero-based array indexing, which would be inconvenient in Eiffel. But we don't need to do that at all anyway, because calculating it at each step is completely redundant: we can just do a final subtraction at the end, right?
